The Basics of Ska

I'm going to jam with some locals tonight who play a lot of ska. The problem is; I don't really know how to play ska music too well. I know what ska is and listen to it often, but when it comes to playing it on guitar, im kind of in the dark about it.

I know about upstrokes, bar chords, and somewhat the beats and timings ska is often in, and I've been looking at tabs and whatnot and it seems I can pick it up fairly quick, but my question is:Is there any basics or things that I will surely need to know whilst jamming tonight? Any essential things I should know? Maybe a couple of fairly easy songs I could pull out and play?

I didn't really find this anywhere in the search bar, so excuse if something similar has already been posted or if this is in the wrong forum.